The following system of equations is represented by the matrix equation $\text{A}\left[\begin{array} {ccc} x \\ y \\ z \end{array} \right]=\vec{b}$. $\begin{aligned}10x+13y+15z&=4 \\12x-2y+5z&=-8 \\2x+2y-6z&=4\end{aligned}$ ${A}=$ $\vec{b}=$ Represent each row and column in the order in which the variables and equations appear.
Solution: The Strategy A system of equations can be represented by a matrix equation $\text{A}\vec{x}=\vec{b}$, where $\text{A}$ is the coefficient matrix, $\vec{x}$ is the variables vector, and $\vec{b}$ is the constants vector. Each row of the matrix equation represents an equation in the system. [I need an explanation, please!] Representing the system of equations as a matrix equation We are given the system of equations: $\begin{aligned}10x+13y+15z&=4 \\12x-2y+5z&=-8 \\2x+2y-6z&=4\end{aligned}$ First, let's rewrite this system to show the coefficients of each variable. $\begin{aligned}{10}x+{13}y+{15}z&=4 \\{12}x+({-2})y+{5}z&=-8 \\{2}x+{2}y+({-6})z&=4\end{aligned}$ Now, the coefficient matrix can be written as follows. $\left[\begin{array} {ccc} {10} & {13} & {15} \\ {12} & {-2} & {5} \\ {2} & {2} & {-6} \end{array} \right]$ We can multiply this matrix by a column vector of variables and set it equal to a column vector with the values on the right side of the equations, as follows. $\left[\begin{array} {ccc} {10} & {13} & {15} \\ {12} & {-2} & {5} \\ {2} & {2} & {-6} \end{array} \right]\left[\begin{array} {ccc} x \\ y \\ z \end{array} \right] =\left[\begin{array} {ccc} 4 \\ -8 \\ 4 \end{array} \right]$ This is our matrix equation. Summary $\text{A}$ and $\vec{b}$ are shown below. $\text{A}=\left[\begin{array} {ccc} 10 & 13 & 15 \\ 12 & -2 & 5 \\ 2 & -2& -6 \end{array} \right]~~~~~~~~~~~~ \vec{b}=\left[\begin{array} {ccc} 4 \\ -8 \\ 4 \end{array} \right]$